Public Vulnerability Reports

Microsoft Excel SLK File Font Parsing Stack Buffer Overflow Vulnerability

14.06.11

BACKGROUND

Excel is the spreadsheet application included with Microsoft Corp.'s Office productivity software suite. More information is available at the following website:

http://office.microsoft.com/excel/

DESCRIPTION

Remote exploitation of a stack-based buffer overflow vulnerability in Microsoft Corp.'s Excel could allow an attacker to execute arbitrary code with the privileges of the current user.

The vulnerability occurs when parsing a font description inside of an SLK file. It is possible to write beyond the bounds of a stack-based buffer, which can corrupt various stack values, including the saved return address. This can allow attackers to execute of arbitrary code.

ANALYSIS

Exploitation of this vulnerability results in the execution of arbitrary code with the privileges of the user opening the file. To exploit this vulnerability, an attacker needs to convince a user to open a malicious file. Attackers typically accomplish this by e-mailing a targeted user the file or hosting the file on a Web page.

DETECTION

The following Microsoft products are vulnerable:

  • Excel 2002 Service Pack 3
  • Excel 2003 Service Pack 3
  • Excel 2007 Service Pack 2
  • Office 2004 for Mac
  • Office 2008 for Mac
  • Office for Mac 2011
  • Open XML File Format Converter for Mac
  • Excel Viewer Service Pack 2
  • Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats Service Pack 2

WORKAROUND

Microsoft recommends the following workarounds:

  • Use Microsoft Office File Block policy to block the opening of Office 2003 and earlier documents from unknown or untrusted sources and locations
  • Use the Microsoft Office Isolated Conversion Environment (MOICE) when opening files from unknown or untrusted sources

VENDOR RESPONSE

Microsoft Corp. has released patches which address this issue. Information about downloadable vendor updates can be found by clicking on the URLs shown.

http://www.microsoft.com/technet/security/bulletin/MS11-045.mspx

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2011-1276 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems.

DISCLOSURE TIMELINE

01/05/2011 Initial Vendor Notification
01/05/2011 Initial Vendor Reply
06/14/2011 Coordinated Public Disclosure

CREDIT

This vulnerability was reported to iDefense by Nicolas Gregoire (www.agarri.fr).

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LEGAL NOTICES

Copyright © 2011 Verisign, Inc.

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Disclaimer: The information in the advisory is believed to be accurate at the time of publishing based on currently available information. Use of the information constitutes acceptance for use in an AS IS condition. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information.